Spas and hot tubs are highly popular and modern home construction often incorporates a hot tub or spa, within the home or exterior of the same and physically mounted on or into a deck or the like. The water within the spa shell is continuously circulated during use, being removed from the interior of the spa shell, subject to reheating and aeration and injected back into the interior of the spa shell. The users of spas and hot tubs desire the water temperature to be relatively high for its therapeutic effect. Heat loss from the water is excessive and attempts have been made to reduce such heat loss. Typically, a thermal insulation spa hard cover overlies the upwardly open spa shell during periods of non-use. The spa shell itself is supported or surrounded by a vertical perimeter skirt panel, with the upper edge of the skirt panel underlying the rim of the spa shell. In the past, a thermal insulation material such as polyurethane has been sprayed onto the exterior surface of the spa shell to reduce heat loss by convection through the spa shell to the exterior. Such urethane coatings, however, have no effect on heat loss in the plumbing connections, i.e. the pipes or tubing associated with the spa support equipment such as pumps, heaters and circulating the water from the interior of the spa shell to the spa support equipment and returning the same for injection interiorly of the spa shell through fittings projecting through the spa shell and opening to the interior of the spa. Thermal insulation of bathtubs, spas and hot tubs has been attempted in the past years. Early bathtubs were formed of cast iron. The heat of water drawn into a cast iron tub of 500 pounds weight may be absorbed by a cold iron tub so fast that before the normal bath is completed, water temperature drops from a comfortable to an uncomfortable temperature. Thus, insulation of the exterior of such a tub is of little value in conserving the heat of the water. The more modern bathtubs formed of steel, enameled steel, plastic have significantly reduced heat convection losses.
U.S. Pat. No. 2,602,935 to H. K. Phillips, issued Jul. 15, 1952 and entitled "INSULATING APPARATUS FOR BATHTUBS" teaches the use of a wire basket configured to the exterior of an upwardly open elongated U-shaped cross-section bathtub supported by hooks depending from the rim of the bathtub and supporting a fibrous insulation material mat in the space between the basket and the outer surface of the tub, with the insulation material held against the outer surface of the tub.
The more modern approach is to spray onto the outer surface of the tub a polyurethane foam insulation coating. Unfortunately, such spray coating covers everything including the water or air and water injection nozzles mounted within the spa shell and coupled to the spa support equipment by typical plumbing connections involving tubing, hoses or the like, particularly for spas and hot tubs. Such spray insulation coatings render repair of leaks, in defective spa support equipment and plumbing connections difficult, if not impossible. Further, such insulation on the exterior surface of the tub, spa shell or hot tub shell has no effect on heat losses emanating directly from the plumbing connections or pipes exterior of the shell itself.
U.S. Pat. No. 4,316,294 to Baldwin, issued Feb. 23, 1982 and entitled "BATHTUB" teaches the formation of a bathtub of a unitary body having an insulated interior formed of wood or pressed wood fibers bonded together by a suitable adhesive with an exposed exterior covering of fiberglass, plastic or the like, and with that exterior covering defining internally a well adapted to comfortably receive the body of the person while considerably reducing the dissipation of heat from the water within the well and which tends to escape by radiation through the body and by radiation and convection outwardly of the bathtub body.
Such construction, while adequate for bathtubs and while providing significant thermal insulation capability, is inapplicable to spas and hot tubs, since all of the plumbing connections are embedded within the wood or pressed wood adhesively bonded fibers.
U.S. Pat. No. 4,357,721 to Newburger, issued Nov. 9, 1982 and entitled "BATHING ASSEMBLY", illustrates the limited use of flexible plastic sheet material in the bathtub field. In this patent, a flexible plastic sheet liner constitutes the interior of the tub. The liner is housed within a cabinet and the cabinet is collapsed beneath a standing sink during non-use of the bathtub. The cabinet structure is expanded to place the flexible plastic film liner into an upwardly open position to function as a bathtub interior wall. The bathing assembly is employed in a hospital or the like where the liner is changed for each patient using the same to prevent a patient from contacting disease from a prior user of the bathing assembly.
U.S. Pat. No. 4,858,254 to Popovich et al., issued Aug. 22, 1989 and entitled "TUB APPARATUS", teaches a tub manufactured from multiple layers of thin plastic films. The laminate structures include foam plastic sheets wound in a spiral about a tub axis to form multiple layers. A tensile liner bonded to the tub wall inner side resists outward expansion in response to loading exerted by liquid filling the tub interior or well. The thermal insulation is effected by a non-stretchable flexible liner, which includes a layer of polyethylene foam bonded to interwoven strips and also to the wall inner side.
The patents to Newburger and Popovich et al. evidence limited use of thin, flexible plastic film material in the construction of tubs, spas and hot tubs.
It is a principal object of the present invention to insulate a spa on site or in the factory to minimize heat loss from the spa by attaching loosely a blanket of thermal insulation material positioned between the outside of the spa shell and the inside of a peripheral wood skirt of panels surrounding the exterior of the spa and extending vertically beneath the rim of the spa shell to the wood skirt panels, to enclose the spa plumbing and to create a dead air space, which effectively reflects heat loss from the interior of the spa shell and from the plumbing back into the well within the spa shell, which permits access to and ready repair of the spa shell or the spa plumbing through the blanket while permitting re-positioning of the blanket after repair of the spa.